Wildlife/Nature Question: What to do with (possible) abandoned eggs in a nest?

Okay…bear with me while I explain.

I live on a river and I care for the wildlife on it as much as I can. I have a predatory heron that comes and eats the young and eats the eggs of the moorhens on the river. Usually the build their nests in the dark brush across the river and then come out to my side when I feed them. Well, a moorhen (a coot in the US), for the first time built a nest on my side of the river which is accessible to all the night animals and the heron. I saw him swallow a whole brood of baby moorhens early one morning when I was awakened by terrified squawking from the mother hen. I could not get downstairs fast enough to stop it. It was quite brutal. I know this is nature, but they are tiny and vulnerable and it was painful for me to watch.

So, the moorhen laid the eggs and I have been watching the nest from a distance. However, in order to feed the other animals, I have to pass by her nest. I do so very quietly and respectfully. She will usually climb out of the nest, swim away and come back. She does this every time I come to feed the rest of the animals,so I didn’t worry. This time, I startled her. She must have been asleep when I walked by. She started squawking and hissing loudly at me and then swam out and then came back and hissed some more and swam away where she watched me. I decided to just walk away quickly.After I came back, I saw her come and look around the nest and then she swam away. I got worried.

About half an hour later, I went to check and she was not back on her nest. She has always seen me and not been startled, so I thought she would be okay.

It is almost nightfall, the eggs are in their nest and I don’t know what to do. If I leave them there overnight, there are predators (foxes, badgers, the heron, cats) that come into the garden. How long do I leave them? Will she just abandon them like that? And if I have to do a rescue, how do you take care of eggs like that so that they will hatch? Should I even take them in? It’s rather chilly in the evenings here.

Any information will be appreciated. Thank you.